The present invention relates to a manufacturing method for a photoreceptor base drum which is applied to various kinds of image recording apparatuses such as an electrophotographic copier, a printer, a facsimile, and the like.
The electrophotographic process is used to record images in recording apparatuses such as an electrophotographic copier, a laser printer, and a digital computer. In the electrophotographic process, an electrostatic latent image is formed on a photoreceptor by exposing a uniformly electrified photoreceptor to light corresponding to the image information. The latent image is developed and transferred to a recording paper. After that, the transferred paper is heated for fusing, and finally the image is formed on the recording paper. Various kinds of materials are used for the photoreceptor. An organic semiconductor with photoconductivity is used by forming a substrate layer, an electric charge generation layer, and an electric charge transport layer in order to form a light-sensitive layer on the surface of a cylindrical drum base which is usually made from nonferrous metals such as aluminum and copper, or nonmetallic materials such as plastics. Furthermore, inorganic light-sensitive materials such as CdS and ZnO on which an insulating layer and a protective layer are coated, or vapor-deposited amorphous selenium and amorphous silicon are used as the photoreceptor materials.
The surface of the drum base must be smooth because electrostatic latent images and visual images are formed on this kind of photoreceptor drum. Recently, the surface of a photoreceptor has been cut by a diamond, tool or a diamond bit to accomplish mirror-finishing. A diamond tool resists abrasion and wears at a low rate because it is hard and can withstand high temperatures. Therefore, the diamond tool can finish each part accurately and make a smooth mirror-finished surface easily, and is suited for cutting the surface of a photoreceptor drum base.
However, in the case of a newly ground diamond tool, a major cutting edge formed by a rake face and a flank and a minor cutting edge formed by the face and a side flank are extremely sharp. In addition, the diamond tool may have defects which occurred during grinding, and scratches on the diamond tool caused in grinding. As a result, while the diamond tool is cutting the photoreceptor drum base, material cut from it tends to form a deposit on the sharp and defective cutting edge while cutting is conducted, and then the cutting edge tends to fall off. It is known that the diamond tool damages the surface to be machined and a good mirror-finished surface can not be obtained for the reasons mentioned above.
Conventionally a dummy material is cut by a diamond tool before it is used, in what is called the break-in. A sharp diamond tool, after being ground, usually cuts a dummy material for the break-in to wear the sharp cutting edge adequately, and then the diamond tool starts mirror-finishing the surface of actual materials. A high quality cutting edge is obtained by cutting a dummy material with the diamond tool for the break-in period to eliminate the defects of the tool which were caused while the tool was being ground. As a result, excellent cutting and burnishing can be conducted on a work surface and a smooth mirror-finished surface can be formed.
However, in order to conduct the break-in cutting of a new diamond tool, it is necessary to cut a substitute work surface with the tool for 10Km to 100Km. Furthermore, it is necessary to change the angle between the tool and the work surface many times during the break-in. In order to get a cutting tool with an efficient cutting edge, a great deal of time and work are needed, which decreases productivity.
It is thus desirable to eliminate the break-in of a cutting tool and to get a high quality cutting edge from the start of cutting. For example, according to Japanese Patent Publication Open to Public Inspection No. 271605/1987, as shown in FIG. 8, it is proposed to install a chamfer with the width of 0.2 to 0.8.mu.m on the major cutting edge which is formed by the face 11a and the front flank 11b of the cutting tool 11. However, the chamfered cutting tool mentioned above can not conduct mirror-finishing on the work surface from the start of cutting, but merely reduces the break-in period, and it also is difficult to form a mirror-finished surface stably on the work surface by this method from the start.
When break-in cutting is not conducted sufficiently or slight scratches are left on the surface of the drum base due to the initial surface conditions of the cutting tool, lubricating oil or minute particles are left in the scratches even after the drum base is washed, or dust in the air sticks in the scratches. When a photoreceptor is made by forming the above-mentioned light-sensitive layer on the drum surface in this condition and it is installed in an apparatus, its image quality is degraded as the scratches on the photoreceptor surface can cause electrical leaks when it is charged or cause image blur or interference fringes when an image is recorded. The light-sensitive layer is generally considered to be better when thinner. But, when the mirror-surface can not be obtained on the surface of the drum base, it is difficult to reduce the thickness of the light-sensitive layer. When the layer is thick, it brings about efficiency degradation.